Conventionally, a semiconductor light emitting element including a plurality of semiconductor layers containing GaN and laminated on a sapphire substrate has been proposed (see e.g. Patent Document 1).
In a known method for manufacturing a semiconductor light emitting element, after semiconductor layers are formed on a sapphire substrate, a support substrate is bonded to the semiconductor layers on the side opposite from the sapphire substrate. Then, the sapphire substrate is removed utilizing heat generated by laser beam irradiation (see Patent Document 2, for example). FIG. 20 shows an example of semiconductor light emitting element manufactured by such a method. In the semiconductor light emitting element X shown in the figure, a p-GaN layer 92, an active layer 93 and an n-GaN layer 94 as semiconductor layers are laminated on a support substrate 91 formed with a p-side electrode 91a. The upper surface of the n-GaN layer 94 is formed with an n-side electrode 94a. The active layer 93 amplifies the light emitted by the recombination of electrons injected from the n-GaN layer 94 and holes injected from the p-GaN layer 92. For instance, the active layer 93 has a Multiple Quantum Well (hereinafter referred to as “MQW”) structure. The semiconductor light emitting element X is designed to emit light from the upper surface of the n-GaN layer 94 and the side surface 97 of the n-GaN layer 94, active layer 93 and p-GaN layer 92.
Patent Document 1: JP-A-10-012916
Patent Document 2: JP-A-2003-168820
However, due to the potential difference in the thickness direction of the n-GaN layer 94, the electrons injected from the n-side electrode 94a are likely to pass through the n-GaN layer 94. Thus, sufficient current does not flow to the end of the n-GaN layer 94. Thus, it is difficult to cause the recombination of electrons and holes to occur at the entire region of the active layer 93. As a result, in the semiconductor light emitting element X, the efficient light emission for the power applied is difficult, so that high brightness is not achieved.
Moreover, GaN, which forms the n-GaN layer 94, the active layer 93 and the p-GaN layer 92, has a relatively high index of refraction of about 2.5. Thus, the critical angle with respect to air is about 23°, which is relatively small. The light rays which become incident on the side surface 97 at an angle larger than this critical angle are totally reflected and not emitted to the outside of the semiconductor light emitting element X. Thus, in the semiconductor light emitting element X, only a small part of light produced by the active layer 93 is emitted to the outside, so that high brightness is not achieved.